IDEC-Y2B8 (IDEC-103) is a murine IgG1 kappa monoclonal antibody and IDEC- C2B8 (IDEC-102) is a chimeric igG1 kappa monoclonal antibody, with mouse variable and human constant regions. Both antibodies recognize and show specificity for the CD20 antigen expressed on normal B cells and most malignant B-cell lymphomas. High-dose safety studies in cynomolgus monkeys have revealed no adverse clinical events with either antibody, and there were no significant abnormalities on laboratory tests or on histopathology.